GaN-MOVPE气相自由基反应的量子化学研究

摘要/Abstract

摘要： 利用量子化学的密度泛函理论(DFT),对TMG/NH₃/H₂体系中自由基参与的金属有机气相外延(MOVPE)反应进行计算分析,特别针对H、NH₂自由基对Ga(CH₃)₃(简称TMG)热解路径、氢解路径以及加合路径的影响进行研究。通过计算不同反应路径的吉布斯自由能差ΔG和能垒ΔG^*/RT,确定了自由基参与的气相反应在不同温度下不同的反应路径。研究发现:当T<683 K时,TMG与NH₃反应生成加合物TMG:NH₃。当T>683 K时,TMG:NH₃重新分解为TMG和NH₃。TMG在MOVPE温度下很难直接热解,在H自由基作用下则易热解产生Ga(CH₃)₂(简称DMG)、GaCH₃(简称MMG)和Ga原子。当T<800 K时,TMG与NH₃的氨基反应速率大于自由基参与的热解反应,故氨基反应占主导;当T>800 K时,自由基参与的TMG热解反应速率大于氨基反应,故热解反应占主导。氢解反应由于能垒很高,因此可忽略。TMG及其热解产物与NH₂自由基反应很容易产生氨基物。氨基物DMGNH₂可以与H自由基继续反应,最终生成表面反应前体GaNH₂。

关键词: GaN, MOVPE, 密度泛函理论, 自由基, 气相反应

Abstract: The gas-phase reactions involved with radicals in the TMG/NH₃/H₂ system of MOVPE process were studied by the density functional theory (DFT) of quantum chemistry. In particular, the effects of H and NH₂radicals on the pyrolysis, hydrogenolysis and adduct paths of Ga(CH₃)₃ (denoted as TMG) were studied. By calculating of the Gibbs energies ΔG and energy barriers ΔG^*/RT of different reaction paths, the roles of radicals on the reaction paths at different temperatures were determined. The study found that when T<683 K, TMG reacts with NH₃ to generate TMG:NH₃. When T>683 K, TMG:NH₃ decomposes back into TMG and NH₃. At MOVPE condition TMG is difficult to pyrolyze directly. While with H radicals involved, TMG can be easily pyrolyzed into Ga(CH₃)₂(denoted as DMG), GaCH₃(denoted as MMG) and Ga atom. When T<800 K, the rate of amide reaction between TMG and NH₃ is greater than the rate of pyrolysis with H radicals, the reaction is dominated by amide reaction. When T>800 K, the rate of pyrolysis with H radicals is greater than the rate of amide reaction, the reaction is dominated by pyrolysis with H radicals. Since the energy barrier of hydrogenolysis is rather high, the reaction can be ignored. TMG and its pyrolysis products can react with NH₂ radicals easily to produce amide DMGNH₂. The amides can further react with H radicals and eventually generate GaNH₂ as surface reaction precursors.

Key words: GaN, MOVPE, DFT, radical, gas reaction

中图分类号:

TN304.2

刘国峰, 左然. GaN-MOVPE气相自由基反应的量子化学研究[J]. 人工晶体学报, 2021, 50(3): 469-476.

LIU Guofeng, ZUO Ran. Quantum Chemistry Study on Gas Reactions Involved with Radicals in GaN-MOVPE Process[J]. Journal of Synthetic Crystals, 2021, 50(3): 469-476.

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